The present invention relates to a device for detecting the position of an elevator car. The present invention further relates to a method for operating an elevator system exhibiting an elevator car.
Generally known from prior art are generic devices, wherein in particular generic strips typically extending along an elevator shaft, and hence along the traveling direction of the elevator car, are also generally known as carriers for a magnetic coding used for determining the position and/or speed of the elevator car. For example, DE 10 2009 054 337 A1 of the Applicant depicts a generic device in which the carriage-like sensor housing that can move along the strip exhibits the sensor and evaluator unit in the form of suitable magnetic field sensors as well as allocated decoding and evaluator electronics, and makes the electronic signal generated in this way available to other downstream control units.
In particular in conjunction with safety-relevant elevator technology, it is both known and common to allocate such a generic sensor and evaluator unit to a respective elevator car (for passengers or freight) in the outer region of the car. During elevator operation, the (relatively or absolutely provided) magnetic coding on the strips stationary relative to the sensor housing are continuously scanned to generate the respective data, making it possible to determine the position, and from that derive the speed of the elevator car.
Emergency systems of an elevator system must also be presumed as prior art. A typical emergency system of this kind provides that a critical operational and movement state of the elevator car, such as when a speed threshold (possibly depending on a current position) is exceeded, automatically trigger safety measures, for example initiate a braking function for the elevator motor or activate a parachute brake for the elevator car.
Because special importance is here attached to detection reliability, the sensor and evaluator units are usually redundant, i.e., designed as two functional units, which are essentially provided and operated parallel to and independently of each other. The latter can each activate the emergency function in response to reaching a speed threshold, for example.
Despite the described and presumed generically known technology for detecting the speed and position of an elevator car relative to a (stationary and typically magnetized or otherwise coded) strip, it still continues to be common practice in elevator systems technology to safeguard functionalities relevant to safety by means of mechanical switches or similar aggregates. One such case involves setting up so-called safety or cutout positions for an elevator car in a shaft during maintenance operations: If a maintenance technician is on the floor of the elevator shaft during such maintenance operations, a suitable (key) switch is typically operated to activate a mechanical, stationary limit switch that can be actuated via the elevator car, and is positioned in the shaft in such a way as to stop an elevator car moving down via an emergency shutdown, once the latter (upon reaching the switch) threatens to reach or drop below a free minimum height in the shaft as a safety distance for the person. However, such mechanical limit switches require a lot of maintenance and pose a potential risk of malfunctions or the like, with the associated risk to maintenance personnel. Such minimum safety distances are here used both in a lower (floor) elevator shaft region and in an upper shaft region (then as a free area between an elevator car ceiling and an upper shaft end); the safety distances are here also traditionally maintained by stationary mechanical switches provided on the shaft.
Another potential way to achieve safety-relevant optimization in realizing and operating elevator systems involves providing protection against malfunctions (and hence possible endangerment of elevator car passengers) at respective stopping positions along the shaft: These stopping positions typically correspond to the respective floors, so that the passengers can enter or exit the elevator car when the elevator car door is open. The elevator car is here held at the respectively provided position by corresponding braking means. However, inadvertent movements by the elevator car with the car stopped and door open can at the same time result in dangerous situations, for example if the drive and/or brake defects cause the car to not be held precisely in the vertical position or to inadvertently move.
Therefore, the object of the present invention is to improve a generic device for detecting the position of an elevator car in terms of drive and maintenance reliability of an elevator system realized therewith, in particular to ensure additional safety during elevator operation with the car stopped (and car door open), and/or enhance the safety for individuals involved in maintenance in the elevator shaft during maintenance operations for an elevator system. In this case, in particular an equipment or hardware outlay must be minimized, the potentially hazardous traditional mechanical sensors or switches must be minimized, and the ability to monitor such devices must generally be improved.